The use of pharmaceutical aerosols and pressurized medicinal dispensers for inhalation administration of medicaments to a patient is commonplace and becoming increasingly even more important.
The medicament is generally formulated with one or more propellants (e.g. chlorofluorocarbons and more recently hydrogen-containing fluorocarbons, including hydrofluoroalkanes, such as propellant 134a (CF3CH2F) and propellant 227 (CF3CHFCF3), as well as any additional excipients or components, and then charged in a container or vial.
The container is typically fitted by means of a ferrule with a dispensing valve, in particular a metered dose dispensing valve, comprising an elongate outlet member or valve stem movable between closed and dispensing positions, to provide a dispensing canister. The dispensing canister is typically used in conjunction with an adaptor, typically having a patient port, for example a mouthpiece or a port adapted for nasal use. In conventional dispensers, such as a conventional press-and-breathe inhaler, the adaptor typically comprises a support block having a socket adapted to receive the valve stem of the dispensing valve and an orifice having open communication with the socket and the patient port.
With conventional dispensing valves, the valve stem is typically biased to its closed position with the valve stem extending outwardly relative to the container (an “outer” closed position) and to actuate or fire the valve, the valve stem is depressed inwardly to the dispensing position (an “inner” dispensing position) allowing a dose to be dispensed. For example, with a conventional press-and-breathe device, the patient fires the device by depressing the container towards the support block of the adaptor and thus depressing the valve stem inwardly, while inhaling.
Some dispensing valves, for example certain embodiments of shuttle-type metered dose dispensing valves disclosed in U.S. Pat. No. 5,772,085, do not operate in the conventional push-to-fire manner. Instead the valve stem moves relative to the container from an inner closed or priming position to an outer dispensing position. In other words, the dispensing valve is actuated or fired upon movement of the valve stem outwardly relative to the container. The operation of such valves would typically require the user to depress the valve stem inwardly to the priming position and then release to allow firing during the release stroke upon the outward movement of the valve stem to the dispensing position.